Seismic data processing involves converting wave signals into a visual map of the earth’s surface. Explosions or vibrating machines create waves that are received by geophones or hydrophones. Seismic software performs calculations and generates two- and three-dimensional representations of the area. Deconvolution, mute function, and velocity analysis filters are used to clean up the image. Geophysicists can determine the density, porosity, and fluid saturation of the substrate based on travel time, wave velocity, and the number of reflected waves.
Seismic data processing involves compiling, organizing and converting wave signals into a visual map of areas beneath the earth’s surface. The technique requires point tracking and interference elimination. Once upon a time, seismic processing required sending information to a distant computer lab for analysis. Currently, laptop computers equipped with seismic software allow geophysicists to enter and manipulate data on site.
Explosions from explosives or vibrating machines that occur during hydrocarbon exploration or petroleum geology studies produce waves that travel through the ground and can cause it to move. Marine geology studies employ air guns that create pressure waves. Surrounding these devices is a series of geophones or hydrophones, which receive the waves reflected from the subsoil, convert them into an electrical signal and record the reception time. A specific area could receive hundreds or thousands of explosions over a predetermined period of time.
Processing the raw seismic data obtained from geophones requires the software to perform calculations based on distance, time and velocity. As a computer processes the seismic data, the points are plotted on two- and three-dimensional graphs. These coordinates often represent the distance from a sound producing device to the geophones. Other points represent the travel time of the wave from its point of origin to the geophones. The display also shows the depth reached by the waves before reflecting on the surface.
After collecting the raw data and making the required calculations, seismic data processing software can generate a two-dimensional reflection plot. By performing geometric calculations based on depth and time, the program can create a three-dimensional representation of the area. Geologists might also use colors to indicate various depths or to distinguish between layers. Often these images require fine-tuning.
Deconvolution, in seismic data processing, shortens the reflection waves and reduces ghosting that can occur due to instrumentation, reverberations, or multiple reflections. This feature generally shows more clearly defined levels. The mute function eliminates areas consisting mainly of noise or possibly refractions superimposed on reflections. Velocity analysis filters clean up the image by differentiating between an actual wave signal and noise, based on the frequency and velocity of the wavelet.
Using travel time, wave velocity, and the number of reflected waves, geophysicists can determine the density, porosity, and fluid saturation of the substrate. The denser the rock formation, the faster the waves travel, and porous rock slows the travel of the waves. Similarly, waves pass rapidly through water-filled areas, but slowly through pockets of air or gas.
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